In Kevin Crossley-Holland’s Norse Myths: Tales of Odin, Thor and Loki, Tyr loses his hand to Fenrir.
The episode comes from the traditional Norse story of the wolf Fenrir, whose growing strength alarms the gods. They try to bind him with chains, but Fenrir breaks them. The gods then use Gleipnir, a magical fetter made from unusual ingredients, and Fenrir agrees to the test only if one of them places a hand in his mouth as a pledge.
Tyr accepts the risk. When Fenrir discovers that Gleipnir cannot be broken and realizes the gods intend to keep him bound, he bites down and severs Tyr’s hand. The event explains Tyr’s later one-handed depiction and emphasizes his courage and commitment to an oath.
Tyr is sometimes confused with Odin because both are associated with wisdom, war, and authority. Odin does not lose a hand in this myth; Tyr does.